The present invention pertains to the field of jet technology, primarily to liquid-gas ejectors for producing a vacuum during evacuation of various gaseous and gas-vapor mediums.
An ejector is known, which includes a steam nozzle, a mixing chamber converging in the flow direction and having a throttle, and a diffuser (see, Sokolov E. Y. and Zinger N. M., xe2x80x9cJet Apparatuses, Moscowxe2x80x9d, xe2x80x9cEnergoatomizdatxe2x80x9d Publishing house, 1989, pages 94-95).
Ejectors of this type are widely adopted for evacuation of gas-vapor mediums in the condenser units of steam turbines and in steam-ejector refrigeration units.
However the efficiency of these ejectors is relatively low in cases where the evacuated gaseous mediums contain a lot of condensable components.
The closest analogue of the ejector described in the invention is a liquid-gas ejector having a liquid nozzle and a mixing chamber (see, Sokolov E. Y. and Zinger N. M., xe2x80x9cJet Apparatusesxe2x80x9d, Moscow, xe2x80x9cEnergoatomizdatxe2x80x9d Publishing house, 1989, pages 213-214).
Such ejectors are used in power engineering as air-ejector devices of condenser units, in water deaeration vacuum systems, and for vacuumization of various reservoirs. One characteristic of the given ejectors is the fact that during evacuation of a steam-air mixture the steam, contained in the mixture, is condensed and therefore a water-air mixture is compressed in the mixing chamber (if water is used as the liquid medium fed into the nozzle).
But the operational effectiveness of these ejectors is not high enough. A relatively low performance of the ejectors is often caused by nonoptimal correlation between the regime of nozzle liquid flow and the minimal sectional area of the mixing chamber.
The objective of the present invention is to increase the efficiency factor of a liquid-gas ejector due to optimization of the correlation between the regime of nozzle liquid flow and the minimal sectional area of the mixing chamber.
The stated objective is achieved as follows: the minimal cross-sectional area of a mixing chamber of a liquid-gas ejector, having a nozzle and the mixing chamber, is determined from the following formula:   F  =      kQ    ⁢                            Pc          *          g                γ            
where
Fxe2x80x94area of the minimal cross-section of the mixing chamber;
kxe2x80x94design factor;
Qxe2x80x94volumetric flow rate of a liquid through the nozzle;
gxe2x80x94acceleration of gravity;
xcex3xe2x80x94density of the liquid fed into the nozzle;
Pcxe2x80x94liquid pressure at the nozzle inlet;
The k factor has a value ranging from 1.6 to 60 when the ratio of the liquid pressure at the nozzle inlet to the pressure of a mixture of mediums at the mixing chamber outlet ranges from 1.4 to 25. The k factor has a value ranging from 60 to 2200 when the ratio of the liquid pressure at the nozzle inlet to the pressure of a liquid-gas mixture at the mixing chamber outlet ranges from 25 to 5000.
Experimental research has shown, that correlation between the areas of minimal cross-sections of the mixing chamber and the nozzle does not give firm confidence for an optimal operational mode of the liquid-gas ejector, because the correlation does not take into account the energy impulse transferred from the high-speed liquid flow to the evacuated gaseous medium. It is borne in mind that the liquid flow through the same nozzle may vary and, consequently, such flow parameters as the degree of the liquid flow dispersion behind the nozzle outflow face and the flow velocity at the nozzle outflow face may be different. In its turn, dimensions of the mixing chamber, and above all an area of its minimal cross-section, depend on the mentioned flow parameters. The experiments helped to discover a dependence between the area of the minimal cross-section of the mixing chamber and the major operational parameters of the ejector nozzlexe2x80x94liquid pressure at the nozzle inlet and liquid flow rate through the nozzle. In addition, a design factor was discovered, whose value, in its turn, depends on the ratio between the liquid pressure at the nozzle inlet and pressure of a liquid-gas mixture at the mixing chamber outlet. So, the following dependence between the stated above parameters was obtained:   F  =      kQ    ⁢                            Pc          *          g                γ            
where
Fxe2x80x94area of the minimal cross-section of the mixing chamber;
kxe2x80x94design factor;
Qxe2x80x94volumetric flow rate of a liquid through the nozzle;
gxe2x80x94acceleration of gravity;
xcex3xe2x80x94density of the liquid fed into the nozzle;
Pcxe2x80x94liquid pressure at the nozzle inlet;
As for the design factor k its value amounts from 1.6 to 60 when the ratio of the liquid pressure at the nozzle inlet to the pressure of mediums"" mixture at the mixing chamber outlet is from 1.4 to 25 and the k factor ranges from 60 to 2200 when the ratio of the liquid pressure at the nozzle inlet to the pressure of mediums"" mixture at the mixing chamber outlet is from 25 to 5000.